Okay, I can expand further, but that will make this cluttered view even more cluttered.. So.. Where do I go from here? I can of course guess, but that should not be necessary. I think I personally only need one little hint and hopefully an explanation to that one and I'll be able to solve the rest.

In column 3, 8 can only go in box 7(r7c1-r9c3) so you can eliminate 8 in other cells in box 7. So r7c1 - {4,5} and r7c2 - {1,2,4,5}

r7c1 - {4,5}, r7c3 - {1,4,8}, r7c4 - {1,5,8}, r7c8 - {1,5,8}

Naked quadruple. I don't know why there are so many of these lately. Basically 4 cells have possibilities made up with combination only 4 numbers, {1,4,5,8}. So you know these 4 numbers will go into these 4 cells. We don't know exactly what number goes into which cell but we know what numbers we can eliminate on OTHER cells in row 7.

So after eliminating 1, 4 and 5 from r7c2, we get 2 in that cell.

You can also say that this is hidden pair of 7 and 9 in row 7. Usually naked quadruple can be solved as hidden pair. But to me, it was always easier to spot the naked <something> than hidden <something>.

Nacked quadruple - they are very nice.
You could solve it also without them:

4 not in r3c1, it is in r1c1 or r1c3 (Row on 3x3 Block interaction)
4 not in r3c2, it is in r1c1 or r1c3 (Row on 3x3 Block interaction)
8 not in r7c1, it is in r7c3 or r8c3 (Column on 3x3 Block interaction)
8 not in r7c2, it is in r7c3 or r8c3 (Column on 3x3 Block interaction)
8 not in r9c2, it is in r7c3 or r8c3 (Column on 3x3 Block interaction)
1 not in r3c2, it is in r3c7 or r3c8 of the 3x3 (3x3 Block on Row/Column interaction)
1 not in r3c4, it is in r3c7 or r3c8 of the 3x3 (3x3 Block on Row/Column interaction)
2 not in r7c6, Hidden Pair 7 9 in r7c6 and r7c9 (in Row)
5 not in r7c6, Hidden Pair 7 9 in r7c6 and r7c9 (in Row)
8 not in r7c6, Hidden Pair 7 9 in r7c6 and r7c9 (in Row)
2 in r7c2 - Unique Horizontal